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United States Patent |
5,548,269
|
Katsuno
,   et al.
|
August 20, 1996
|
Chip resistor and method of adjusting resistance of the same
Abstract
A chip resistor is provided which comprises an insulating chip substrate, a
resistor element formed on the chip substrate, a first pair of electrode
terminals branching out from one end of the resistor element, and a second
pair of electrode terminals branching out from the other end of the
resistor element. One of the first pair electrode terminals is a current
terminal while the other of the first pair electrode terminals is a
voltage terminal. Similarly, one of the second pair electrode terminals is
a current terminal, and the other of the second pair electrode terminals
is a voltage terminal.
Inventors:
|
Katsuno; Takafumi (Ukyo-ku, JP);
Kambara; Shigeru (Ukyo-ku, JP)
|
Assignee:
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Rohm Co. Ltd. (Kyoto, JP)
|
Appl. No.:
|
313922 |
Filed:
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September 26, 1994 |
Foreign Application Priority Data
Current U.S. Class: |
338/325; 338/195; 338/308; 338/332 |
Intern'l Class: |
H01C 001/12; H01C 001/148 |
Field of Search: |
338/325,332,195-308
|
References Cited
U.S. Patent Documents
3772631 | Nov., 1973 | Owen | 338/195.
|
4032881 | Jun., 1977 | Singleton | 338/195.
|
4294648 | Oct., 1981 | Brede et al. | 338/308.
|
4418474 | Dec., 1983 | Barnett | 338/195.
|
4904850 | Feb., 1990 | Claypool et al. | 219/548.
|
5015989 | May., 1991 | Wohlfarth et al. | 338/195.
|
5051719 | Sep., 1991 | Gaston et al. | 338/162.
|
5065221 | Nov., 1991 | Imamura | 257/538.
|
5198794 | Mar., 1993 | Sato et al. | 338/195.
|
5212466 | May., 1993 | Yamada et al. | 338/22.
|
5285184 | Feb., 1994 | Hatta et al. | 338/313.
|
Foreign Patent Documents |
24134572 | Sep., 1975 | DE | .
|
2834207 | Feb., 1980 | DE | .
|
2904197 | Aug., 1980 | DE | .
|
3616217 | Apr., 1987 | DE | .
|
3811854 | Oct., 1989 | DE | .
|
94030278 | Jun., 1994 | DE | .
|
Other References
Delfs, H.: Hybridschaltungen, Abgleichverfahren fur Widerstande. In:
Internationale Elektronische Rundschau 1971, Nr. 8, S. 195-199.
AEG Hilfsbuch Fur elektronische Licht-und Kraftanlagen der allgemeinen
Elektricitats-Gesellschaft, 7. Aufl., S. 300-303; 1956.
JP 4-139701 A., In: Patents Abstracts of Japan, E-1257, Sep., 2, 1992, vol.
16, No. 415.
|
Primary Examiner: Walberg; Teresa J.
Assistant Examiner: Valencia; Raphael
Attorney, Agent or Firm: Bednarek; Michael D.
Claims
We claim:
1. A chip resistor comprising:
an insulating chip substrate;
a resistor element formed on the chip substrate;
a first pair of electrode terminals branching out from one end of the
resistor element, one of the first pair of electrode terminals being a
current terminal, the other of the first pair of electrode terminals being
a voltage terminal; and
a second pair of electrode terminals branching out from the other end of
the resistor element, one of the second pair of electrode terminals being
a current terminal, the other of the second pair of electrode terminals
being a voltage terminal;
wherein at least one of the electrode terminals of the first and second
pairs is formed with a trimmed portion extending along the resistor
element at least at one end thereof.
2. The chip resistor according to claim 1, further comprising:
at least one additional resistor element formed on the chip substrate;
a third pair of electrode terminals branch out from one end of said
additional resistor element; and
a fourth pair of electrode terminals branch out from the other end of said
additional resistor element.
3. The chip resistor according to claim 1, wherein the electrode terminals
of the first and second pairs are located respectively at the four corners
of a rectangle, the current terminal of the first pair being located
diagonally opposite to the current terminal of the second pair, the
voltage terminal of the first pair being located diagonally opposite to
the voltage terminal of the second pair.
4. The chip resistor according to claim 3, wherein the resistor element
extends generally diagonally of said rectangle from the current terminal
of the first pair toward the current terminal of the second pair.
5. The chip resistor according to claim 2, wherein the electrode terminals
of the first pair are located at a first side of said rectangle, whereas
the electrode terminals of the second pair are located at a second side of
said rectangle which is opposite to said first side.
6. The chip resistor according to claim 3, wherein the current terminal of
the first pair and the voltage terminal of the second pair are located at
a first side of said rectangle, whereas the voltage terminal of the first
pair and the current terminal of the second pair are located at a second
side of said rectangle which is opposite to said first side.
7. A current detecting circuit incorporating a chip resistor which
comprises: an insulating chip substrate; a resistor element formed on the
chip substrate; a first pair of electrode terminals branching out from one
end of the resistor element, one of the first pair of electrode terminals
being a current terminal, the other of the first pair of electrode
terminals being a voltage terminal; and a second pair of electrode
terminals branching out form the other end of the resistor element, one of
the second pair of electrode terminals being a current terminal, the other
of the second pair of electrode terminals being a voltage terminal; at
least one of the electrode terminals of the first and second pairs being
formed with a trimmed portion extending along the resistor element at
least at one end thereof; wherein
the current terminals of the first and second pairs are electrically
connected to a current supplying source; and
the voltage terminals of the first and second pairs are electrically
connected to a voltage detector.
8. A current detecting method performed by using a chip resistor which
comprises: an insulating chip substrate; a resistor element formed on the
chip substrate; a first pair of electrode terminals branching out from one
end of the resistor element, one of the first pair of electrode terminals
being a current terminal, the other of the first pair of electrode
terminals being a voltage terminal; and a second pair of electrode
terminals branching out from the other end of the resistor element, one of
the second pair of electrode terminals being a current terminal, the other
of the second pair of electrode terminals being a voltage terminal; at
least one of the electrode terminals of the first and second pairs being
formed with a trimmed portion extending along the resistor element at
least at one end thereof; wherein the method comprising the steps of:
supplying a current across the current terminals of the first and second
pairs; and
measuring a voltage drop across the voltage terminals of the first and
second pairs.
9. A method of adjusting a resistance of a chip resistor which comprises:
an insulating chip substrate; a resistor element formed on the chip
substrate; a first pair of electrode terminals branching out from one end
of the resistor element, one of the first pair of electrode terminals
being a current terminal, the other of the first pair of electrode
terminals being a voltage terminal; and a second pair of electrode
terminals branching out from the other end of the resistor element, one of
the second pair of electrode terminals being a current terminal, the other
of the second pair of electrode terminals being a voltage terminals;
wherein the method comprising the steps of:
supplying a known current across the current terminals of the first and
second pairs;
measuring a voltage drop across the voltage terminals of the first and
second pairs; and
trimming at least one of the electrode terminals of the first and second
pairs along the resistor element at least at one end thereof until the
measured voltage drop reaches a predetermined value.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a chip resistor which can be suitably used for
detecting a small current. The present invention also relates to a current
detecting circuit and method utilizing such a chip resistor. The present
invention further relates to a method of adjusting the resistance of such
a resistor.
2. Description of the Related Art
As is well known, chip resistors are used in various applications and have
proven to enable high integration (high-density mounting). For the
convenience of description, reference is now made to FIGS. 17 through 20
showing three different prior art chip resistors.
As shown in FIGS. 17 and 18, a typical prior art chip resistor comprises an
insulating chip substrate a on which a resistor element b is formed by
printing a resistor material paste. The resistor element b is connected
endwise to a pair of electrode terminals c formed by printing a conductive
paste. Further, the resistor element b is covered by a glass coating d for
protection.
FIG. 19 shows another prior art chip resistor which differs from the
resistor of FIGS. 17 and 18 only in that it comprises a shorter resistor
element b. Such a chip resistor is advantageously usable as a current
detector in a protection circuit for a DC/DC converter for example because
it is capable of providing a low resistance of say 0.1.OMEGA..
FIG. 20 shows a further prior art chip resistor wherein a very narrow
resistor element b is formed of a conductive paste integrally with
electrode terminals c by simultaneous printing. Apparently, the resistor
element b made of a conductive paste is suitable for providing a very low
resistance.
According to either one of the prior art arrangements, the resistance of
the chip resistor is determined for resistance adjustment by the so-called
"four terminal method" as shown in FIG. 21. In FIG. 21, reference sign R1
represents the resistance of the resistor element b, whereas reference
signs R2, R3 indicate the respective resistances of the two electrode
terminals b.
As shown into FIG. 21, voltage detecting probes p are brought into contact
with the respective electrode terminals c. In this condition, a current of
a known value is allowed to flow across the electrode terminals c, and the
voltage drop across the voltage detecting probes p is measured.
According to the method described above, since the two electrode terminals
c are used for supplying the current and for detecting the voltage drop,
it is impossible to determine the resistance of the resistor element b
alone. Indeed, the measured voltage drop only represents the sum of the
resistances R1, R2, R3. Further, since the resistances R2, R3 (which are
very small) of the electrode terminals c are influenced not only by the
conditions of thick film printing but also by solder deposits used for
mounting the chip resistor, it is extremely difficult to equalize the
resistance characteristics from one chip resistor to another.
The above-describe problem is particularly remarkable when the chip
resistor is intended for providing a very low resistance because the small
resistances R2, R3 of the electrode terminals c become more significant in
determining the overall resistance of the chip resistor. Further,
difficulty is also encountered when using the chip resistor as a detector
for accurately measuring a small current.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a chip
resistor whose resistance can be accurately adjusted and which can be
suitably used for detecting a small current.
The present invention also seeks to provide a current detecting circuit
incorporating such a chip resistor.
The present invention further seeks to provide a method of detecting a
current by using such a chip resistor.
Moreover, the present invention additionally aims to provide a method of
adjusting the resistance of such a resistor.
According to one aspect of the present invention, there is provided a chip
resistor comprising: an insulating chip substrate; a resistor element
formed on the chip substrate; a first pair of electrode terminals
branching out from one end of the resistor element, one of the first pair
electrode terminals being a current terminal, the other of the first pair
electrode terminals being a voltage terminal; and a second pair of
electrode terminals branching out from the other end of the resistor
element, one of the second pair electrode terminals being a current
terminal, the other of the second pair electrode terminals being a voltage
terminal.
According to a preferred embodiment of the present invention, the electrode
terminals of the first and second pairs are located respectively at the
four corners of a rectangle. In such an embodiment, the current terminal
of the first pair is located diagonally opposite to the current terminal
of the second pair, whereas the voltage terminal of the first pair being
located diagonally opposite to the voltage terminal of the second pair.
Preferably, the resistor element may extend generally diagonally of the
rectangle from the current terminal of the first pair toward the current
terminal of the second pair. Such an inclination of the resistor element
eliminates sharp bends of the current path, thereby reducing thermal
damage at the bends.
The electrode terminals of the first pair may be located at a first side of
the rectangle, whereas the electrode terminals of the second pair may be
located at a second side of the rectangle which is opposite to the first
side. Alternatively, the current terminal of the first pair and the
voltage terminal of the second pair may be located at a first side of the
rectangle, whereas the voltage terminal of the first pair and the current
terminal of the second pair may be located at a second side of the
rectangle which is opposite to the first side.
It is also advantageous that the chip resistor further comprise at least
one additional resistor element formed on the chip substrate; a third pair
of electrode terminals branch out from one end of said additional resistor
element; and a fourth pair of electrode terminals branch out from the
other end of said additional resistor element.
According to another aspect of the present invention, there is provided a
current detecting circuit incorporating a chip resistor which comprises:
an insulating chip substrate; a resistor element formed on the chip
substrate; a first pair of electrode terminals branch out from one end of
the resistor element, one of the first pair electrode terminals being a
current terminal, the other of the first pair electrode terminals being a
voltage terminal; and a second pair of electrode terminals branch out from
the other end of the resistor element, one of the second pair electrode
terminals being a current terminal, the other of the second pair electrode
terminals being a voltage terminal; wherein the current terminals of the
first and second pair are electrically connected to a current supplying
source; and the voltage terminals of the first and second pair are
electrically connected to a voltage detector.
According to a further aspect of the present invention, there is provided a
current detecting method performed by using a chip resistor which
comprises: an insulating chip substrate; a resistor element formed on the
chip substrate; a first pair of electrode terminals branch out from one
end of the resistor element, one of the first pair electrode terminals
being a current terminal, the other of the first pair electrode terminals
being a voltage terminal; and a second pair of electrode terminals branch
out from the other end of the resistor element, one of the second pair
electrode terminals being a current terminal, the other of the second pair
electrode terminals being a voltage terminal; wherein the method comprises
the steps of: supplying a current across the current terminals of the
first and second pairs; and measuring a voltage drop across the voltage
terminals of the first and second pairs.
According to still another aspect of the present invention, there is
provided a method of adjusting a resistance of a chip resistor which
comprises: an insulating chip substrate; a resistor element formed on the
chip substrate; a first pair of electrode terminals branch out from one
end of the resistor element, one of the first pair electrode terminals
being a current terminal, the other of the first pair electrode terminals
being a voltage terminal; and a second pair of electrode terminals branch
out from the other end of the resistor element, one of the second pair
electrode terminals being a current terminal, the other of the second pair
electrode terminals being a voltage terminal; wherein the method comprises
the steps of: supplying a known current across the current terminals of
the first and second pairs;
measuring a voltage drop across the voltage terminals of the first and
second pairs; and trimming at least one end of the resistor element until
the measured voltage drop reaches a predetermined value.
Other objects, features and advantages of the present invention will be
fully understood from the following detailed description given with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a plan view showing a chip resistor according to a first
embodiment of the present invention;
FIG. 2 is a perspective view showing the same resistor;
FIG. 3 is a circuit diagram showing how the resistance of the same resistor
is determined and adjusted;
FIG. 4 is a circuit diagram showing how to use the same resistor for
detecting a current;
FIG. 5 is a plan view showing a chip resistor according to a second
embodiment of the present invention;
FIG. 6 is a circuit diagram showing one use of the chip resistor
illustrated in FIG. 5;
FIG. 7 is a circuit diagram showing another use of the chip resistor
illustrated in FIG. 5;
FIG. 8 is a plan view showing a chip resistor according to a third
embodiment of the present invention;
FIG. 9 is a plan view showing a chip resistor according to a fourth
embodiment of the present invention;
FIG. 10 is a plan view showing a chip resistor according to a fifth
embodiment of the present invention;
FIG. 11 is a plan view showing a chip resistor according to a sixth
embodiment of the present invention;
FIG. 12 is a plan view showing a chip resistor according to a seventh
embodiment of the present invention;
FIG. 13 is a perspective view showing the chip resistor of FIG. 12;
FIG. 14 is a plan view showing a chip resistor according to an eighth
embodiment of the present invention;
FIG. 15 is a plan view showing a chip resistor according to a ninth
embodiment of the present invention;
FIG. 16 is a plan view showing a chip resistor according to a tenth
embodiment of the present invention;
FIG. 17 is a plan view showing a prior art chip resistor;
FIG. 18 is a sectional view taken along lines XVIII--XVIII in FIG. 17;
FIG. 19 is a plan view showing another prior art chip resistor;
FIG. 20 is a plan view showing still another prior art chip resistor; and
FIG. 21 is a circuit diagram showing how to use the prior art resistor for
current detection.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Throughout the accompanying drawings, like parts are designated by the same
reference signs for clarifying the relation between different embodiments
of the present invention.
Referring first to FIGS. 1 and 2, there is shown a chip resistor according
to a first embodiment of the present invention. The chip resistor,
represented by reference numeral 1, comprises an insulating chip substrate
1 made of a ceramic material such as alumina. In the illustrated
embodiment, the chip substrate 1 is generally rectangular or square, but
it may be otherwise shaped.
The chip substrate 1 has an upper surface formed with a resistor element 3.
A pair of electrode terminals 4a, 4b branch out from one end of the
resistor element 3 toward one side of the chip substrate 2. A similar pair
of electrode terminals 4a, 4b branch out from the other end of the
resistor element 3 toward the opposite side of the chip substrate 2. Of
the four electrode terminals, two terminals represented by reference sign
4a are used as current terminals, whereas the other two terminals 4b are
used as voltage terminals.
According to the first embodiment, the four electrode terminals 4a, 4b are
located at the respective corners of a rectangle. The two current
terminals 4a are positioned diagonally opposite to each other, as also are
the two voltage terminals 4b. Such an arrangement is preferred because the
chip resistor 1 may be symmetrically mounted to a circuit board to assume
180.degree. opposite orientations, thereby facilitating handling of the
chip resistor 1 for surface mounting.
The resistor element 3 and the respective electrode terminals 4a, 4b may be
integrally formed of a conductive paste such as silver-palladium paste or
silver paste deposited by thick film printing. Even if a conductive paste
is used, the resistor element 3 may be made to have a low resistance of
0.01-1.00.OMEGA. by greatly decreasing its width and by selecting a
suitable length for it.
As shown in FIG. 2, each of the electrode teminals 4a, 4b has a side
extension 4a', 4b' and a rear extension 4a", 4b". The rear extension 4a",
4b" comes into electrical contact with a corresponding electrode pad (not
shown) of a circuit board upon surface mounting of the chip resistor 1.
For adjusting the resistance of the resistor element 3, trimmed portions 5
formed by partial removal of the conductive paste may be provided at least
at one end of the resistor element 3. Apparently, the trimmed portions 5
increase the effective length of the resistor element B to change its
resistance.
The upper surface of the chip substrate 2 is covered by a protective
coating 6 in a manner such that the four electrode terminals 4a, 4b remain
exposed. The protective coating 6 may be made of glass for example.
In manufacture, use is made of a master ceramic plate (not shown), as
usually practiced for making conventional chip resistors. The master plate
is formed with a plurality of longitudinal and transverse cutting lines
(scribed lines for example) later used for division into a plurality of
unit chip substrates 2. Thick film printing is first performed for
simultaneously forming resistor elements 3 and electrode terminals 4a, 4b
(see FIGS. 1 and 2) with respect to all of the sections corresponding to
the unit chip substrates 2. Then, the master plate is divided into the
unit chip substrates by cutting along the cutting lines. After division of
the master plate, side extensions 4a', 4b' and rear extensions 4a", 4b"
are formed for the respective unit chip substrates 2 in a conventional
manner.
The electrical resistance of the resistor element 3 of each chip resistor 1
thus obtained is determined and adjusted by the so-called "four terminal
method", as described below.
FIG. 3 shows an equivalent circuit for resistance measurement. The
resistance of the resistor element 3 is represented by reference sign R1.
Further, the respective internal resistances of the current terminals 4a
are represented by reference signs R2, R3, whereas the respective internal
resistances of the voltage terminals 4a are represented by reference signs
R4, R5.
As shown in FIG. 3, for resistance determination and adjustment, current
probes P1 are brought into contact with the respective current terminals
4a, whereas voltage detecting probes P2 are brought into contact with the
respective voltage terminals 4b. In this condition, a current of a known
value is allowed to flow between the current terminals 4a, and the voltage
drop across the voltage detecting probes P2 is measured. Laser trimming 5
(see FIG. 1) may be performed until the measured voltage drop reaches a
predetermined target value which corresponds to the desired resistance for
the resistor element 3.
According to the method described above, little current flows through the
respective voltage terminals 4b because these terminals are provided
separately from the current terminals 4b through which most of the current
flows. Thus, the voltage drop across the voltage detecting probes P2
substantially corresponds to the voltage drop across the resistor element
3. As a result, it is possible to accurately measure and adjust the
resistance R1 of the resistor element 3 despite the inherent internal
resistances of the current terminals 4a. Apparently, this is a remarkable
improvement over the prior art (see FIG. 21) wherein the sum of the
resistances R1, R2, R3 is inevitably measured.
In this way, the resistance R1 of the resistor element 3 can be accurately
measured and adjusted. Therefore, it is possible to equalize the
resistance characteristics from one chip resistor to another, thereby
increasing the production yield.
The chip resistor 1 may be used as a current sensor in a current detecting
circuit for example. Such an application is now described with reference
to FIG. 4.
In FIG. 2, the chip resistor 1 is shown to be incorporated in a current
detecting circuit 7. When the current detecting circuit 7 is used for
current detection in a DC/DC converter for example, the current terminals
4a are connected to a current supplying source, whereas the voltage
terminals 4b are connected to a voltage detector 8. Reference signs R6-R9
in FIG. 4 represent internal resistances present in the current detecting
circuit 7. Reference signs R10, R11 represent internal resistances present
in the voltage detector 8.
With the circuit arrangement described above, the resistance R1 of the
resistor element 3 is accurately known (determined). Therefore, by
measuring the voltage drop across the resistor element 3 (R1), it is
possible to accurately determine the current through the resistor element
B according to the Ohm's law. At this time, little current flows in a path
containing the voltage detector 8, so that the internal resistances R4, R5
of the voltage terminals 4b give only negligible influence on the voltage
drop measurement.
In this way, since the voltage terminals 4b are provided separately from
the current terminals 4a, it is possible to exclude the adverse influences
which might be caused by the internal resistances R2, R3 of the current
terminals 4 in determining the current through the resistor element 3.
In addition to the advantages described above, the chip resistor 1 is also
advantageous in that it can be conveniently mounted on the surface of the
circuit board and enables high integration together with other circuit
elements on the same circuit board.
FIG. 5 shows a chip resistor 1 according to a second embodiment of the
present invention. The chip resistor 1 of this embodiment comprises an
elongated chip substrate 2 for carrying two resistor elements 3 in
parallel to each other. Each of the resistor elements 3 is equally
associated with a set of four electrode terminals 4a, 4b and covered by a
common protective glass coating 6. The chip resistor 1 of the second
embodiment is otherwise the same as that of the first embodiment.
The chip resistor 1 of the second embodiment may be used in different ways.
Assuming now that each of the resistor elements 3 has a resistance of
0.1.OMEGA. for example, the chip resistor 1 as a whole may be used to
provide a resistance of 0.1.OMEGA. by using only one of the resistor
elements 3, as shown in FIG. 6. On the other hand, the chip resistor 1 can
also provide a resistance of 0.5.OMEGA. by connecting the two resistor
elements 3 in parallel to each other, as shown in FIG. 7. Apparently, a
resistance of 0.2.OMEGA. is also obtainable by connecting the two resistor
elements 3 in series (not shown).
FIG. 8 shows a chip resistor 1 according to a third embodiment of the
present invention. The chip resistor 1 of this embodiment is similar to
that of the first embodiment (FIG. 1) but differs therefrom only in the
following points.
First, two electrode terminals 4a, 4b branching out from each end of a chip
element 3 extend toward two opposite sides of the chip substrate 2, as
opposed to the first embodiment (see FIG. 1) wherein the two electrode
terminals 4a, 4b branching out from each end of the resistor element 3
extend to a common side of the chip substrate 1. Secondly, the resistance
of the chip element 3 is adjusted by two trimmed portions 5 which are
respectively formed at the opposite ends of the resistor element 3 by
laser trimming.
FIG. 9 shows a chip resistor 1 according to a fourth embodiment of the
present invention. The chip resistor 1 of this embodiment is similar to
that of the first embodiment (see FIG. 1) but differs therefrom only in
that the resistance of the chip element 3 is adjusted by two trimmed
portions 5 which are respectively formed at the opposite ends of the
resistor element 3 by laser trimming.
FIG. 10 shows a chip resistor 1 according to a fifth embodiment of the
present invention. The chip resistor 1 of this embodiment is similar to
that of the third embodiment (see FIG. 8) but differs therefrom only in
that two trimmed portions 5 are formed at each end of the resistor element
3 for providing a total of four trimmed portions.
FIG. 11 shows a chip resistor 1 according to a sixth embodiment of the
present invention. The chip resistor 1 of this embodiment is similar to
that of the first embodiment (see FIG. 1) but differs therefrom only in
that a resistor element 3 is formed separately from the respective
electrode terminals 4a, 4b. The resistor element 3 may be made of a
resistor material paste such as ruthenium oxide paste. Though not
illustrated in FIG. 11, the resistance of the resistor element 5 may be
adjusted by laser trimming.
Apparently, the use of the resistor material paste widens the range of
resistance obtainable by the resistor element 3. Further, the resistor
element 3 may be made to have a relatively large width.
FIGS. 12 and 13 show a chip resistor 1 according to a seventh embodiment of
the present invention. The chip resistor 1 of this embodiment is similar
to that of the third embodiment (see FIG. 8) but differs therefrom only in
that a resistor element 3 is formed generally diagonally of the chip
substrate 2 from one current electrode terminal 4a to the other.
According to the seventh embodiment, the resistor element 3 extends
diagonally or obliquely to minimize the degree of bends in the current
path. Thus, it is possible to reduce local thermal damage which might be
caused by current concentration at the bends of the current path, thereby
prolonging the service life of the chip resistor 1 while increasing the
operating reliability of the chip resistor.
FIG. 12 shows a chip resistor 1 according to an eighth embodiment of the
present invention which is similar to the second embodiment (see FIG. 5).
Specifically, the chip resistor 1 of the eighth embodiment comprises an
elongated chip substrate 2 for carrying two resistor elements 3 which are
obliquely formed but arranged in parallel to each other. Each of the
resistor elements 3 is equally associated with a set of four electrode
terminals 4a, 4b and covered by a common protective glass coating 6.
Like the second embodiment, the chip resistor 1 of the eighth embodiment
may be used in different ways. Either one of the resistor elements 3 may
be used (see FIG. 6) for utilizing a full resistance of that resistor
element. Alternatively, the two resistor elements B may be connected in
parallel for halving the resistance (see in FIG. 7), or in series for
doubling the resistance.
FIG. 15 shows a chip resistor 1 according to a ninth embodiment of the
present invention. The chip resistor 1 of this embodiment is similar to
that of the seventh embodiment (see FIG. 12) but differs therefrom only in
that a resistor element B is formed separately from the respective
electrode terminals 4a, 4b by using a resistor material paste such as
ruthenium oxide paste.
FIG. 16 shows a chip resistor 1 according to a tenth embodiment of the
present invention. The chip resistor 1 of this embodiment is similar to
that of the seventh embodiment (see FIG. 12) but differs therefrom only in
that two electrode terminals 4a, 4b branching out from each end of an
oblique chip element 3 extend toward a common side of the chip substrate
2, as opposed to the seventh embodiment (see FIG. 12) wherein two
electrode terminals 4a, 4b branching out from each end of the resistor
element 3 extend to two opposide sides of the chip substrate 1.
The present invention being thus described, it is obvious that the same may
be varied in many ways. Such variations are not to be regarded as a
departure from the spirit and scope of the present invention, and all such
modifications as would be obvious to those skilled in the art are intended
to be included within the scope of the following claims.
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